The present invention relates a hot gas flue pipe.
More particularly, this invention relates to a hot gas flue pipe assembly suitable for installation inside a boiler, the pipe assembly having an inner pipe and an outer pipe and wherein the latter is in heat-conducting contact or relationship, along a portion of its integral length, with the inner pipe so that the heat conducting contact is attained by means of circumferential contact deformations disposed at least in sub-zones of the outer pipe.